Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.
The pilot took off at around 08:15 from a private helipad in Montauroux (Var). He stopped at Fayence aerodrome (Var) to pick up a passenger, and then headed in the direction of Saint-Raphaël.
Whilst he was flying over a hill north-east of Saint-Raphaël at a height of around 500 ft, witnesses heard a reduction in the engine’s power then saw the main rotor blades spinning slowly. They then saw the ultralight descend and pick up speed. The ultralight collided with the ground. A fire broke out upon impact.
One of the two intake pressure sensors in the air manifold sent erroneous values to the engine parameter display computer. An error message without voice alarm was then displayed on the instrument panel instead of the engine parameters, without the governing of the engine being altered. The investigation was unable to determine what caused the failure of this sensor.
The pilot probably started an autorotation and lowered the collective pitch lever. The engine rotation speed then continuously decreased until the end of the flight.
Given the low height and the unfavourable surrounding environment, the pilot did not manage to complete an autorotation in total safety. The ultralight collided with the vegetation, then the ground.